Transcript Biogenesis – 14.1 - Leavell Science Home

Evolution
Biogenesis
Abiogenesis
Before the 1600s,
it was generally
thought that
organisms could
arise from
nonliving
material by
spontaneous
generation
Francesco Redi
Redi showed in 1668
that rotting meat kept
away from flies would
not produce new flies
Maggots appeared
only on meat that had
been exposed to flies
Lazzaro Spallanzani
Spallanzani showed in the 1700s that
microorganisms would not grow in broth when its
container was heated and then sealed
This seemed to indicate that microorganisms that
cause food spoilage do not arise from spontaneous
generation but, rather, are carried in the air
Louis Pasteur
Pasteur used a
variation of
Spallanzani’s
design to prove that
microorganisms are
carried in the air
and do not arise by
spontaneous
generation
Fossil Record
Fossils
A fossil is a trace of a long-dead organism
The law of superposition states that new geologic
strata are deposited on top of older strata
The history of Earth and its life-forms can be
inferred by examining the fossil record
Fossil Record
The fossil record
shows that new lifeforms have arisen
continually during the
history of life on Earth
Biogeography
The study of
biogeography shows
that organisms arise
in areas where
similar, now-extinct
organisms once lived
Theories of Evolution
Jean Baptiste de Lamarck
Lamarck proposed that
species evolve over time
He incorrectly hypothesized
that species modification is
the result of acquired
characteristics and that these
characteristics can be passed
on to offspring
Charles Darwin began his work on evolution
when he was employed as a naturalist for a
voyage of the H.M.S. Beagle
Uniformitarianism
Darwin was influenced
by Charles Lyell, who
proposed the principles
of uniformitarianism,
which hold that the
structure of Earth
results from cycles of
observable processes
Adaptive Radiation
Darwin found evidence of species
modification in both modern and extinct
species
Darwin hypothesized that related species,
such as the Galapagos finches, descended
from a common ancestor
Natural Selection
Darwin wrote The
Origin of Species,
in which he
proposed that
natural selection is
the principal
driving force
behind evolution
Adaptation
A population of
organisms adapt to
their environment as
their proportion of
genes for favorable
traits increases
So what exactly is evolution?
Evolution is the change in genetic makeup
of a population over generations
Can you create the perfect habitat
for each of these wild canines?
HOMEWORK!!!
Using magazine clippings, crayons,
and markers, illustrate a habitat you
think each canine is well suited for.
Life in the Grasslands…
The maned wolf is well
adapted for life in the tall
grass plains or pampas of
South America. Their
stilt-like legs aren't for
running -- this canine is
no speedster. Instead,
long legs help maned
wolves peer over tall
grasses to spot each other
and their prey.
Life in the Desert…
The fennec fox makes its
home in the desert. Pale fur
reflects the sun's rays, and
extends over the soles of its
paws to protect against
burning desert sands.
When fennec foxes
overheat, they shunt or
send blood to their large
ears to rapidly dump the
excess body heat into the
environment.
Life in the Arctic…
Not many wild canines can survive the
frigid temperatures of the arctic. The arctic
fox is the only year-round small canine
resident of this harsh environment. Its fur
goes from white in winter to brown-gray in
summer, keeping in line with the seasonal
change from white snow cover to brown
tundra. To keep warm, it has thick fur that
even covers the soles
of its feet and tiny
ears to reduce heat
loss when the
temperature dips
far below zero.
Life in the Forest…
The gray fox has a unique adaptation for life in the forest.
In addition to small body size and short legs that make it
easy to move through the underbrush, the gray fox is the
only climbing canine. Using its somewhat curved claws, it
scampers up trees to avoid predators as well as to forage
for food such birds or their eggs.
Evolution in Process
Body Structures
Evidence supporting evolution is found in the body
structures of living organisms
Homologous structures have a common structure
Analogous structures are similar in function but have
different structure
A species with vestigial structures probably shares
evolutionary origins with a species that has a functional
forms of the structure
Homologous Structures
Analogous Structures
Vestigial Structures
Embryological & Molecular Evolution
Similar embryological
development among
species indicates a common
evolutionary history
Similarity in
macromolecules such as
RNA, DNA, and proteins
indicates a common
evolutionary history
Coevolution
In coevolution, two or
more closely
associated species,
such as a predator and
its prey, change in
response to each other
Convergent Evolution
In convergent
evolution,
organisms that
are not closely
related resemble
each other
because they
have responded
to similar
environments
Divergent Evolution
In divergent evolution, related populations become less
similar as they respond to different environments
Adaptive radiation is a type of divergent evolution
Disruption of Genetic Equilibrium
Genetic Equilibrium Shifts
Evolution can take place if the genetic
equilibrium of a population is disrupted
Immigration
 Nonrandom mating
 Genetic drift
 Stabilizing selection
 Directional selection
 Disruptive selection
 Sexual selection

Immigration & Emigration
Immigration can bring new genes into a
population, causing evolution
Emigration is the movement of individuals
out of a population
Nonrandom Mating
Nonrandom
mating can alter
the genotypes of a
population, but
does not affect
allele frequencies
Genetic Drift
Genetic drift
operates in small
populations; the
contribution or lack
of contribution of the
genes of one or a few
organisms can
change the
population’s gene
pool significantly
Stabilizing Selection
Stabilizing
selection
encourages the
formation of
average traits
Directional Selection
Directional selection
encourages the formation of
more-extreme traits, such as a
very long tongue in anteaters
Disruptive Selection
Disruptive selection selects for extreme
traits rather than average traits
Sexual Selection
In sexual selection,
the development of
traits that may seem
harmful can actually
enhance reproductive
fitness if they
encourage mating
Formation of Species
Species Definition
According to the
biological species
concept, a species is a
population of organisms
that can successfully
interbreed and cannot
breed with other groups
Speciation
Speciation means
species formation,
and it always
begins with a
population that has
become isolated
Geographic Isolation
Geographic isolation results from the
division of an original population
Reproductive Isolation
Reproductive isolation results from barriers
to successful breeding
Prezygotic isolation occurs
before fertilization
Postzygotic isolation occurs after
fertilization and results in wasted gametes